酸、Cd胁迫对宽叶雀稗种子萌发、幼苗生长及亚细胞结构的影响

Effects of acid and cadmium stresses on seed germination,seedling growth,and subcellular structure of Paspalum wettsteinii

为研究宽叶雀稗(Paspalum wettsteinii)对酸和Cd胁迫可能存在的特殊响应策略,以宽叶雀稗种子为试验材料,采用培养皿滤纸法,设置不同酸(pH为5.5、4.5、3.5)和Cd(5、10、20 mg·L-1)胁迫浓度,测定不同胁迫条件下宽叶雀稗种子萌发、幼苗生长及亚细胞结构等指标。结果表明:酸胁迫对宽叶雀稗种子发芽率具有促进作用,其中pH 4.5具有显著促进作用;pH 3.5处理对宽叶雀稗种子的发芽势、发芽指数、活力指数、根长、芽长和生物量等指标具有抑制作用,其他酸胁迫处理则与对照(纯水处理)无显著差异(P>0.05);Cd胁迫条件下宽叶雀稗的发芽率、发芽势和发芽指数均与对照无显著差异(P>0.05),活力指数、芽长、根长和生物量均随Cd胁迫浓度的增加呈显著降低趋势(P<0.05);pH 3.5和10 mg·L-1Cd胁迫均会对根尖质膜和芽的亚细胞结构造成严重损伤,出现淀粉粒肿胀、断裂,细胞器解体和细胞空泡化等现象。研究表明,宽叶雀稗种子对酸和Cd胁迫有一定的耐性,轻度胁迫会促进种子萌发和幼苗生长。

The species Paspalum wettsteinii is widely grown in acidified and cadmium(Cd)-contaminated soil in Changting Rare Earth Mine, Fujian Province. The species might have special adaptive strategies to acid and Cd stresses. Therefore, an experiment was carried out to evaluate seed germination, seedling growth, and subcellular structure of P. wettsteinii under different stress conditions,namely, acid(pH5.5, 4.5, and 3.5)and Cd stresses(5, 10, and 20 mg·L-1). The results showed that acid stress promoted seed germination, and the pH 4.5treatment had a significant growth promoting effect. The pH 3.5 treatment exhibited inhibitory effects on germination potential, germination index, vigor index, root length, bud length, and biomass of P. wettsteinii seedlings, whereas the effects of other acid stress treatments were not significantly different from those of the control(P>0.05). The germination rate, germination potential, and germination index of the seeds under Cd stress were not significantly different from those of the control(P>0.05), and the vigor index, bud length, root length, andbiomass decreased significantly with the increase in Cd concentration(P<0.05). Both pH 3.5 and 10 mg·L-1 Cd induced serious damage to the plasmalemma of root tip cells and subcellular structure of buds, resulting in starch granule swelling, fracture, cell organelle disintegration, and cell vacuolation. The results revealed that the seeds of P. wettsteinii are tolerant to acid and Cd stresses, and mild stress could promote seed germination and seedling growth.